Increasing oil production

ABSTRACT

A method of recovering petroleum from dormant oil wells or increasing the production of oil wells. An alkali metal or alkaline earth metal carbonate is introduced into a water layer associated with a subterranean petroleum reservoir and/or an explosive composition is introduced into an oil layer associated with a subterranean petroleum reservoir. CO 2  gas is produced by reacting the alkali metal or alkaline earth metal carbonate with an acid and/or by detonating the explosive composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of application Ser. No. 12/275,719 filedon Nov. 21, 2008, which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to revitalization of dormant oil wells andincreased petroleum productions of oil wells by artificialpressurization.

BACKGROUND

Oil wells are formed from boreholes drilled into a porous, subterraneanrock formation containing petroleum. These porous, subterranean rockformations are referred to as petroleum reservoirs or oil reservoirs.Often, a petroleum reservoir is located beneath a less permeable rocklayer that traps the reservoir under pressure. In reservoirs under newlydeveloped production, pressure naturally present within the reservoirprovides force to allow for the migration of petroleum from thepetroleum bearing rock into the borehole forming the oil well. As an oilwell produces, pressure subsides until a point is reached whereproduction is no longer economically sustainable, and the oil well istypically abandoned.

An abandoned oil well can potentially contain over half of the originalamount of oil in the reservoir; however, a lack of pressure in thereservoir makes continued operation of the oil well economicallyunproductive without further intervention. Several secondary andtertiary recovery methods have been used to recover additional oil. Onemethod is to inject water or a gas (such as CO₂ or nitrogen) into thereservoir to create additional pressure. Polymers and surfactants havealso been employed to lower the viscosity of petroleum remaining in thereservoir and aid in petroleum flow. However, such methods are typicallycostly or potentially impractical in cases where materials are expensiveand/or large amounts of water are not locally available.

SUMMARY

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intended toneither identify key or critical elements of the invention nor delineatethe scope of the invention. Its sole purpose is to present some conceptsof the invention in a simplified form as a prelude to the more detaileddescription that is presented later.

The compositions and methods disclosed herein provide for a low-costrecovery of additional petroleum from sleeping wells as well as enhancedthe petroleum production from active wells in an economically efficientmanner. Pressure in the form of CO₂ gas is generated by detonating anexplosive and by reacting a carbonate or bicarbonate compound with anacid. The acid, typically in the form of a mineral acid, also serves toacidify a water layer or aquifer associated with the petroleumreservoir. The solubility of CO₂ gas in water is reduced at low pH.Therefore, acidification of any water present in the vicinity of thepetroleum reservoir allows a greater fraction of generated CO₂ gas tocontribute to pressurizing the petroleum reservoir rather thanunproductively dissolving into water. A wide range of explosives can beused to practice the methods disclosed herein. The explosive can be asolid, liquid, gel, or a slurry, although free flowing explosives willassist in the introduction of the explosive into the petroleumreservoir. Typical explosive compositions employed in the invention areformed from separate fuel and oxidizer mixed together. The explosive canbe carbon rich as to maximize CO₂ production and minimize waterproduction during combustion.

One aspect of the invention is directed toward methods to increasepetroleum production from an oil well drilled into a petroleum reservoirhaving an oil layer and an aqueous layer. One or more of an alkalicarbonate or an alkaline earth carbonate is delivered into the waterlayer through an injection well drilled into the water layer. All wellsdrilled into the reservoir are sealed in a manner to substantiallyconfine pressure build-up within the reservoir. An acid is deliveredthrough an injection well drilled into the aqueous layer to react withthe alkali carbonate or alkaline earth carbonate to generate CO₂ gas.

Another aspect of the invention is directed toward use of an explosivecomposition to increase CO₂ pressure within a petroleum reservoir. Anexplosive composition is delivered into the oil layer through aninjection well or production well drilled into the oil layer. An acid isdelivered through an injection well drilled into the water layer toacidify the water and reduce solubility of CO₂. The explosive isdetonated to generate CO₂ gas and heat.

Another aspect of the invention is direct toward methods to increasepetroleum production by using particles of an alkali carbonate or analkaline earth carbonate have an average diameter less than about 100 μmas the alkali carbonate or an alkaline earth carbonate delivered to thewater layer or as additional source of CO₂ gas included in the explosivecomposition.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a representation of a subterranean petroleum reservoir withwells placed therein in accordance with one aspect of the invention.

FIG. 2 is a flow chart of illustrative acts of methods for increasingpetroleum production in accordance with another aspect of the invention.

FIG. 3 is a flow chart of illustrative acts of methods for increasingpetroleum production in accordance with an aspect of the invention.

DETAILED DESCRIPTION

Petroleum deposits are typically located in subterranean, porous rockformations wherein the porous rock is overlaid with a less porous rockformation preventing the escape of petroleum to the surface. The layerof less porous rock is often referred to as cap rock. In addition topreventing the escape of petroleum, the cap rock also prevents gasesproduced from the transformation of organic matter into petroleum. Assuch, untapped, virgin petroleum deposits are often under considerablepressure.

The pressure present in untapped petroleum deposits assists in theefficient extraction of petroleum from deposits. An oil well typicallyconsists of a jacketed borehole drilled through the cap rock and intothe petroleum bearing rock. Perforations are formed in the jacket andthe natural pressure within the petroleum bearing rock causes themigration of petroleum into the borehole. The pressure within thepetroleum deposit can be sufficient to create an oil gusher. Largeblowout preventers are often required to prevent overpressure from thepetroleum reservoir from damaging sensitive equipment. As the petroleumdeposit produces, pressure naturally decreases as petroleum is removedfrom the deposit. Often, high pressure is initially maintained due tothe elution of gasses from liquid petroleum or pressure from waterlayers or aquifers located underneath many petroleum deposits. In allsituations, the rate of petroleum production from a well slows overtime.

The rate of production necessary for continued economical operation is afunction of operation costs, taxes and/or royalties, and oil commodityprice. Abandonment of a well is the economically preferable course ofaction when the amount of money made from oil production is below theassociated costs (operation costs and taxes). As oil production slows,it is possible to attempt to increase production through the use ofvarious secondary and tertiary techniques to increase production rate;however, all such techniques also increase operation costs. Secondaryand tertiary techniques are aimed at either increasing pressure withinthe petroleum deposit to increase production rate or to decrease theviscosity of petroleum remaining within the deposit. Injection of waterand/or gas, polymers, and thermally enhanced recovery methods areexamples of common, but often costly, techniques.

The innovations disclosed herein are directed toward the efficientproduction of CO₂ within a petroleum deposit to revive an abandoned wellor to increase production of an existing well. CO₂ pressure isintroduced into a petroleum deposit by means of an explosive engineeredto produce a maximum release of CO₂ within a sealed oil well. Fuel forthe explosive can be provided by materials located on-site at apetroleum production operation, such as unrefined crude oil, tar, andparaffin waxes, which may be more efficiently employed to increaseproduction rate than the value obtained for such materials on themarket. That is, the value of increased petroleum production exceeds theprice of such materials on the open market, thereby, allowing oilproduction to be increased with minimal associated cost.

The innovations disclosed herein are directed toward artificialproduction of CO₂ within a subterranean petroleum reservoir. One aspectof the innovation is directed toward generation of CO₂ gas by additionof an alkali or alkaline earth carbonate compound and a mineral acid toa water layer or aquifer associated with the subterranean petroleumreservoir and reacting the alkali or alkaline earth carbonate with anacid. Another aspect of the innovation is directed toward generation byacidification of a water layer or aquifer associated with thesubterranean petroleum reservoir and adding an explosive compositioncontaining an alkali or alkaline earth carbonate followed by detonationof the explosive composition.

Due to the need to generate pressure, the size of the reservoir ispreferably not an overly vast size. In one embodiment, the volume withinthe porous rock of the petroleum reservoir is less than about 10 km³. Inanother embodiment, the volume within the porous rock of the petroleumreservoir is less than about 10 km³. In yet another embodiment, thevolume within the porous rock of the petroleum reservoir is less thanabout 1 km³.

Formation of Explosive Composition

The explosive compositions useful in practicing the invention contain atleast the two following components: a fuel source and an oxidizer. Inanother embodiment, the explosive composition contains a fuel source, anoxidizer, and an emulsifying agent. In yet another embodiment, theexplosive composition contains a fuel source, an oxidizer, anemulsifying agent and an alkali or alkaline earth carbonate compound.

In one embodiment, the fuel source can be selected from one or more ofcarbon powder, unrefined crude oil, unrefined crude oil originating fromthe oil well to be revitalized, tar derived from crude oil, refineddiesel fuel, lubricating oil, heavy gas oil, and paraffin waxes. Otherfuel sources can also be used provided that sufficient combustionoccurs. In another embodiment, the fuel source is a carbon powder or a“hydrocarbon-based” compound, or a mixture thereof, wherein the term“carbon powder” refers to amorphous carbon and/or graphite and the term“hydrocarbon-based” refers to compounds formed from primarily carbon andhydrogen. In one embodiment of a hydrocarbon-based compound, thecompound contains no hetero atoms (atoms other than carbon and hydrogen)and can contain alkane, alkene, alkyne, cyclic, or aromaticfunctionalities. In one embodiment, the carbon powder has an averageparticle size diameter from about 20 nm to about 1 mm. In anotherembodiment, the carbon powder has an average particle size diameter fromabout 1 μm to about 500 μm. In yet another embodiment, the carbon powderhas an average particle size diameter from about 50 μm to about 300 μm.In another embodiment, the hydrocarbon-based compound contains no morethan about three hetero atoms per 10 carbon atoms. In yet anotherembodiment, the hydrocarbon-based compound contains no more than aboutone hetero atom per 10 carbon atoms.

The oxidizer component of the explosive can be an inorganic or anorganic nitrate, chlorate or perchlorate. In one embodiment, theoxidizer component is ammonium nitrate. In other embodiment, theoxidizer component is selected from one or more of ammonium nitrate,potassium nitrate, hydroxylammonium nitrate, sodium nitrate, calciumnitrate, ammonium chlorate, sodium perchlorate, ammonium perchlorate andlike nitrate, chlorate and perchlorate compounds. In one embodiment, theoxidizer component is supplied in the form of prills.

In one embodiment, the fuel and oxidizer components can be simply mixedtogether thoroughly to form the explosive composition. However, theexplosive can take the form of a liquid, solid, gel, emulsion or mixturethereof. A free flowing explosive composition facilitates introductionof the explosive into a target subterranean oil reservoir. Formation ofa free flowing explosive composition is facilitated by the formation ofseparate organic/oil phase comprised of the energetic fuel source and aphase comprising the oxidizer, through use of an emulsifying agent. Theoxidizer phase can either be aqueous (water-in-oil emulsion) or formedfrom a water-free molten phase (melt-in-oil emulsion).

Typically, an emulsion is formed by adding an emulsifying agent to thefuel component/phase and mixing until homogeneity. Then, the fuel plusemulsifying agent is added to the oxidizer phase and mixed tohomogeneity. In one embodiment, an alkali or alkali earth carbonate isadded to the emulsion formed from fuel, oxidizer, and emulsifying agentand mixed until bulk homogeneity is achieved. Any additional componentsincluding metallic oxidizers and corrosion resistance compounds areadded to the emulsion containing fuel, oxidizer, and emulsifying agent.In a typical emulsion, the fuel phase forms a continuous phase in theemulsion while the oxidizer and/or aqueous phase fauns a discontinuousphase separated from the continuous phase by the emulsifying agent. Thatis, the emulsifying agent forms micro- or nano-sized micelles having aninterior containing the oxidizer and/or aqueous phase. In oneembodiment, the micelles have an average diameter from about 100 nm toabout 1 μm. In another embodiment, the micelles have a diameter fromabout 1 μm to about 100 μm. The small size of the micelles allows fortransport of the micelles into microporous channels within the petroleumreservoir.

Emulsifying agents are amphiphilic compounds having one portion of thecompound being predominately hydrocarbyl in character and anotherportion of the compound being hydrophilic in nature. Useful emulsifyingcompounds include a wide range of amphiphilic compounds including: saltsof carboxylic acids; products of acylation reactions between carboxylicacids or carboxylic anhydrides and amines; and alkyl, acyl and amidederivatives of saccharides (alkyl-saccharide emulsifiers). Salts ofcarboxylic acids can be produced from reacting a largely hydrophobiccompound, containing at least one carboxylic acid functionality, with analkali hydroxide to form a carboxylic acid salt. Products of acylationreactions between carboxylic acids or carboxylic anhydrides and aminescan be produced from reacting a hydrophobic compound, containingcarboxylic acid or carboxylic anhydride functionality, with a primary orsecondary amine-containing compound through an acylation reaction toform an amide. Many carboxylic acid salts suitable for use anemulsifying agent are available commercially, such as sodiummono-oleate, or readily produced from an acid-base reaction between thecorresponding carboxylic acid and sodium hydroxide or similar alkalihydroxide base. Methods for the synthesis of amide compounds are knownin the art, including U.S. Pat. No. 3,219,666, which is herebyincorporated by reference. The hydrophobic compounds useful for reactionwith amines include compounds containing, in addition to at least onehydrocarbyl group, one or more carboxylic acid groups and hydrophobiccompounds that are derivatives of succinic acid, having two carboxylicacid groups, modified with at least one hydrocarbyl group.

The term “hydrocarbyl group” refers to a substituent having largelyhydrocarbon character. In one embodiment of the invention, a hydrocarbylgroup contains about 16 or more carbon atoms. In another embodiment, thehydrocarbyl group contains about 16 to about 32 carbon atoms. In yetanother embodiment, the hydrocarbyl group contains about 32 to about 200carbon atoms. In yet another embodiment, the hydrocarbyl group containsmore than about 200 carbon atoms. In one embodiment of a hydrocarbylgroup, the hydrocarbyl group contains no hetero atoms and can containalkane, alkene, alkyne, cyclic, and/or aromatic functionalities. Inanother embodiment, the hydrocarbyl group contains no more than aboutthree hetero atoms per 10 carbon atoms. In yet another embodiment, thehydrocarbyl group contains no more than about one hetero atom per 10carbon atoms. In still yet another embodiment, the hydrocarbyl groupcontains a monounsaturated alkene functionality and can be oleic acid.Hydrocarbyl groups and compounds having a hydrocarbyl groups includecompositions that are built up from smaller compound. For example, acompound containing from about 2 to about 4 carbon atoms can be reactedwith an amine or sugar, and then the residue of that compound containingfrom about 2 to about 4 carbon atoms can be added to by polymerizationor other chemical modification to have a total number of carbon atomssubstantially congruent with the embodiments described above.

Examples of suitable primary and secondary amines are given by FormulaeI and II, where R is a hydrocarbon group containing from about 1 toabout 24 carbon atoms.H₂N—R  (I)R—NH—R   (II)

Specific examples of suitable primary or secondary amine-containingcompounds include primary monoamines such as methylamine, ethylamine,propylamine, butylamine, octylamine, dodecylamine, and other primaryamines containing from about 1 to about 24 carbon atoms. Examples ofsuitable secondary monoamines include diethylamine, dipropylainedibutylamine, methylbutylamine, ethylhexylamine, and other secondaryamines containing from about 1 to about 24 carbon atoms.

Further examples of suitable primary or secondary amines are given bythe hydroxyl amines of Formulae III and IV and the ether amines ofFormulae V and VI, where R has the same meaning as above, R′ is definedas either an R group or an R group substituted with one or more hydroxylgroups, and x is from about 2 about 15.H₂N—R—OH  (III)R′—NH—R—OH  (IV)H₂N—(RO)_(x)—H  (V)R′—NH(RO)_(x)—H  (VI)

Still further, a suitable primary or secondary amines can be a polyamineas represented by Formula VII, where each R″ group is independentlyeither hydrogen, an R group, or an R group substituted by one or morehydroxyl or amino functionalities, and y is from about 2 to about 10.R″NH—((CH₂)_(y)N)—R₂″  (VII)

The emulsifying agent can also be an alkyl-saccharide emulsifier, whichis herein defined as an alkyl, acyl, ether, carbamide or amidederivatives of a saccharide, which can be a monosaccharide,polysaccharide, or oligosaccharide, formed from a reaction between asaccharide and a compound having a hydrocarbyl group, as describedabove, containing a carboxylic acid, alcohol and/or carbamatefunctionality to from an alkyl, ether, ester, carbamate or amide bondbetween the hydrocarbyl compound and the saccharide. In one embodiment,the alkyl-saccharide emulsifier contains a monosaccharide. In anotherembodiment, the alkyl-saccharide emulsifier contains a saccharide havingfrom about 2 to about 6 saccharide residues. In yet another embodiment,the alkyl-saccharide emulsifier contains a saccharide having from about7 to about 12 saccharide residues.

In one embodiment, the alkyl-saccharide emulsifier contains amonosaccharide or saccharide residue having from about 4 to about 8carbon atoms. In another embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is an aldose or aketose sugar. In yet another embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is a sugar alcoholsuch as sorbitol and/or the alkyl-saccharide emulsifier can be sorbitolmono-oleate. In still yet another embodiment, the alkyl-saccharideemulsifier contains a monosaccharide or saccharide residue that is adehydration product or a sugar and/or sugar alcohol such as 1,4-sorbitanor isosorbide. In a further embodiment, the alkyl-saccharide emulsifiercontains a monosaccharide or saccharide residue that is an amino sugarsuch as glucosamine. Specific illustrative examples of saccharidesinclude fructose, glucose, galactose, erythrose, ribose, deoxyribose,xylose, mannose, sorbose, sorbitol, 1,4-sorbital, isosorbide,polysorbates, allose, mannoheptulose, octolose and stereoisomersthereof.

In one embodiment, the alkyl-saccharide emulsifier contains about onehydrocarbyl group. In another embodiment, the alkyl-saccharideemulsifier contain from about two to about three hydrocarbyl groups.

Many alkyl-saccharide emulsifiers are available commercially. Inaddition, methods of making saccharide-based emulsifiers having analkyl, ether, ester, carbamate or amide bond between the hydrocarbylcompound and the saccharide are known in the art. WO 97/18243, describesthe synthesis of saccharide-based emulsifiers having an ester or amidebond between the hydrocarbyl compound and the saccharide. WO 03/031043describes the synthesis of saccharide-based emulsifiers having an amideor carbamate bond between the hydrocarbyl compound and the saccharide.U.S. Pat. Nos. 5,576,425 and 5,374,715, which are hereby incorporated byreference, describes the synthesis of saccharide-based emulsifiershaving an ether-type bond between the hydrocarby compound and thesaccharide.

In one embodiment, the explosive composition contains from about 2% toabout 10% by weight of a fuel component. In another embodiment, theexplosive composition contains from about 3.5% to about 8% by weight ofa fuel component. The fuel component can be the organic phase of anemulsion. In one embodiment, the explosive composition contains fromabout 90% to about 98% by weight of an oxidizer component or an aqueousphase containing an oxidizer component. In another embodiment, theexplosive composition contains from about 92% to about 96.5% by weightof an oxidizer component or an aqueous phase containing an oxidizercomponent. In one embodiment, the emulsifying agent in the explosivecomposition is from about 4% to about 50% of the total weight of thefuel component and/or the organic phase. In another embodiment, theemulsifying agent in the explosive composition is from about 12% toabout 30% of the total weight of the fuel component or the organicphase. In yet another embodiment, the emulsifying agent in the explosivecomposition is from about 4% to about 5% of the total weight of the fuelcomponent or the organic phase.

The explosive compositions and emulsions disclosed herein do not limitthe invention but only serve to illustrate the breadth of explosivecompositions and emulsions useful in the invention. The particularillustrations above represent suitable explosive compositions that maybe efficiently used at a typical oil well site in view of availabilityof components, cost, and ability to generate CO₂ gas.

The above is not exhaustive of the emulsifying compounds useful formaking suitable explosive compositions. U.S. Pat. Nos. 6,800,154;3,447,981; 3,765,964; 3,985,593; 4,008,110; 4,097,316; 4,104,092;4,218,272; 4,259,977; 4,357,184; 4,371,408; 4,391,659; 4,404,050;4,409,044; 4,448,619; 4,453,989; 4,534,809; 4,710,248; 4,840,687;4,956,028; 4,863,534; 4,822,433; 4,919,178; 4,919,179; 4,844,756;4,844,756; 4,818,309; 4,708,753; 4,445,576; 4,999,062; all of which areincorporated herein by reference, contain teachings regarding suitableemulsifying compounds as well as teachings concerning methods of makingexplosive compositions including ratios of components and additives.

The combination of fuel and oxidizer is selected based on thestoichiometry of a combustion reaction between the fuel component andthe oxidizer compounds forming CO₂ and water as the primary products.The amount of either component typically can vary up to about 15% fromthe amount dictated by stoichiometry; however, some embodiments candeviate further.

In one embodiment, an alkali or alkaline earth carbonate is added to theexplosive composition and mixed until homogeneity is achieved. Weightand percentages of fuel component, oxidizer component, and emulsifyingagent referred to throughout this disclosure refer to weight andpercentages of an explosive composition containing only the fuelcomponent, oxidizer component, emulsifying agent and water included inthe oxidizer/aqueous phase. Alkali or alkaline earth carbonates andother additives, such as metallic oxidizers, can be added to theexplosive composition by mixing. However, the discussion of weight andpercentages of fuel component, oxidizer component, and emulsifyingagent, above, is in reference to the mass of the explosive compositionwithout such additional additives.

The alkali or alkaline earth carbonate serves as an additional source ofCO₂ gas. Alkali or alkaline earth carbonate can decompose into CO₂ gasupon detonation of the explosive composition. Alkali and alkaline earthcarbonates include, but are not limited to, sodium carbonate (soda ash),calcium carbonate, potassium carbonate and magnesium carbonate. Sodiumcarbonate is particularly preferred. The alkali or alkaline earthcarbonate can be supplied as particulate material in the micro or nanosize range. In one embodiment, the average diameter of alkali oralkaline earth carbonate particles is about 100 μm or less. In anotherembodiment, the average diameter of alkali or alkaline earth carbonateparticles is from about 1 to about 100 μm. In yet another embodiment,the average diameter of alkali or alkaline earth carbonate particles isfrom about 500 nm to about 1 μm. In yet another embodiment, the averagediameter of alkali or alkaline earth carbonate particles is from about250 to about 500 nm. In still yet another embodiment, the averagediameter of alkali or alkaline earth carbonate particles is from about400 nm to about 100 μm. In a further embodiment, the average diameter ofalkali or alkaline earth carbonate particles is about 500 nm or less.Throughout this disclosure, micro- or nano-sized particles refersparticles having one of the preceding diameter size restrictions.

Alkali earth carbonates are practically insoluble in water at pH aboveabout 6 and only sparingly soluble at pH from about 4 to about 6.Therefore, particulate alkaline earth carbonate can be mixed into anexplosive composition that is an emulsion with minimal loss ofparticulate material due to alkali or alkali earth carbonate dissolvingin water. However, the aqueous phase of the emulsion can be buffered toa pH where carbonate is sparingly soluble or insoluble is needed.

In one embodiment, the alkali or alkaline earth carbonate compound isadded to the explosive composition such that the ratio of carbonate toother components is from about 1:10 to about 1:2 by weight. In anotherembodiment, the alkali or alkaline earth carbonate compound is added tothe explosive composition such that the ratio of carbonate to othercomponents is from about 1:5 to about 2:5 by weight. In yet anotherembodiment, the alkali or alkaline earth carbonate compound is added tothe explosive composition such that the ratio of carbonate to othercomponents is from about 1:5 to about 2:5 by weight.

Pressurization Through Reaction of Carbonate With an Acid

Referring to FIG. 1, the methods and apparatus of increasing oil wellproduction will be discussed and described. In a typical geologicalformation, an oil reservoir 102 is located underneath a cap 104 ofimpervious rock that prevents petroleum from escaping to the surface.Formation of petroleum within the reservoir 102 displaces water suchthat a typical formation has a water layer 106 located below the lessdense oil layer. A gas cap 108 can form above the oil reservoir 102 andbelow the cap 104, the gas cap can be in situ natural gas or othergasses evolved from the petroleum as petroleum is removed from thereservoir 102, or can be gas artificially introduced. In a typicalformation, bed rock is located below the oil layer 102 and/or waterlayer 106.

A production oil well 110 is drilled from the surface, through the caprock 104, and into a portion of the oil reservoir 102. As describedabove, a well may originally produce oil driven by natural pressurewithin the reservoir with enough pressure to force oil into a storageunit 112. Alternatively, the reservoir may contain enough pressure forthe oil well 110 to produce efficiently, however, a pump 114 may beneeded to provide enough energy for oil to complete the journey from theoil layer 102 to storage unit 112.

Oil production is increased through the combined use of theCO₂-releasing explosive composition and acidification of the water layer106 and introduction of an alkali or alkaline earth compound into thewater layer 106. Components are introduced into the water layer throughan injection well 120 drilled into the water layer 106. More than oneinjection well 120 can be formed to distribute injected componentsthroughout the water layer 106.

In one aspect of the invention, alkali or alkaline earth carbonate isinjected through the injection well 120 into the water layer. Theinjection can be with or without pressure as needed. As discussed,alkaline earth carbonates are at most only sparingly soluble at pHgreater than about 4. Therefore, the alkaline earth carbonate can beinjected as an aqueous slurry. The aqueous portion of the slurry can bebuffered to be slightly basic to prevent formation of CO₂ duringintroduction of slurry through well 120. In another embodiment, thealkali or alkaline earth carbonate can be injected as an about saturatedsolution. In yet another embodiment, the alkali or alkaline earthcarbonate can be injected as a saturated solution in contact with micro-or nano-sized particles of alkali or alkaline earth carbonate. In stillyet another embodiment, the alkali or alkaline earth carbonate isinjected as an about 50% saturated or greater solution. Throughout allmethods and innovations disclosed, solutions of acids and alkali oralkaline earth carbonates injected into the petroleum reservoir cancontain small amounts of corrosion inhibitors to protect metal contactsurfaces. For example, RODINE® 213 cationic corrosion inhibitorsolutions sold by Henkel Corporation can be used. RODINE® 213 is asolution containing substituted keto-amine-hydrochlorides andethoxylated nonylphenols in a base of isopropyl alcohol, propargylalcohol, methyl vinyl ketone, acetone, and acetophenone.

In one embodiment, the slurry of alkali or alkaline earth carbonatecontains from about 5 to about 35% by weight of alkali or alkaline earthcarbonate. In another embodiment, the slurry contains from about 10 toabout 30% by weight of alkali or alkaline earth carbonate. In yetanother embodiment, the slurry contains about 15 to about 35% by weightof alkali or alkaline earth carbonate.

The alkali or alkaline earth carbonate injected into the water layer 106is reacted with an acid to generate CO₂ gas. The acid and carbonatematerial are inject through separate injection wells 120 placed into thewater layer 106. In one embodiment, the alkali or alkaline earthcarbonate is injected into the water layer before the acid is injected.In another embodiment, the acid is injected before the alkali oralkaline earth carbonate is injected. In yet another embodiment, thealkali and alkaline earth carbonate are injected simultaneously.Regardless of the order of addition of alkali or alkaline earthcarbonate, all wells drilled into the oil layer 102 or the water layer106 must be sealed in a manner to substantially contain pressurebuild-up from the production of CO₂ gas. The acid can be a mineral acidincluding hydrochloric and sulfuric acid. The acid reacts with thealkali or alkaline earth carbonate; the small size of the addedcarbonate assists in the reaction between alkali or alkaline earthcarbonate and acid to occur quickly and efficiently. An excess of acidis used to achieve acidification of the water layer 106, which reducesthe amount of CO₂ that dissolves into water and becomes unavailable tocontribute the pressure build-up caused by the generation of CO₂ withinthe reservoir.

In one embodiment, the acid is a mineral acid and is added as solutionthat is about 5 to about 50% concentrated. In another embodiment, theacid is a mineral acid and is added as solution that is about 10 toabout 40% concentrated. In yet another embodiment, the acid is a mineralacid and is added as solution that is about 20 to about 40%concentrated.

Where the alkali or alkaline earth carbonate is added to the water layer106 before the acid, the amount of acid addition can be adjusted todepend upon the pH of the water layer 106. The pH of the water layer 106can be monitored through any well 120 that is remote from the well 120through which acid is being added. Water can be either pumped out fromthe water layer 106 and the pH measured or a pH probe may be placedinside a remote well 120. In one embodiment, the amount of acid added issuch that pH in the water layer is from about 4.5 to about 6.5. Inanother embodiment, the amount of acid added is such that pH in thewater later is from about 5.5 to about 6.5. In another embodiment, theamount of acid added is such that pH in the water layer is from about5.5 to about 6. In yet another embodiment, the amount of acid added issuch that pH in the water layer is from about 4.5 to about 5.5.

Acidification of the water layer 106 decreases the fraction of CO₂ thatdissolves in water in the form of carbonic acid. CO₂ that dissolves inthe water layer 106 is unavailable to contribute to pressure increasewithin the reservoir. In one embodiment, from about 50 to about 100% ofthe carbon in the alkali or alkaline earth carbonate is released as CO₂.In another embodiment, from about 60 to about 85% of the carbon in thealkali or alkaline earth carbonate is released as CO₂. In yet anotherembodiment, from about 35 to about 85% of the carbon in the alkali oralkaline earth carbonate is released as CO₂.

Those skilled in the art will readily understand that the fraction ofalkali or alkaline earth carbonate reacting with acid to form CO₂ gasand/or carbonic acid is ascertainable through use of pH measurement andthe well-known Henderson-Hasselbalch equation, provided that the waterlayer 106 does not contain any significant buffering agents other thanthe alkali or alkaline earth carbonate and enough time has elapsed forthe reaction between acid and alkali or alkaline earth carbonate toreach equilibrium. For example, the pH of the water layer isapproximately 5.44 when 90% of the alkali or alkaline earth carbonatereacts with two equivalents of acid based on a pK_(a) of 6.4 for thebicarbonate ion.

Due to the large volume of a typical petroleum reservoir, a large timelag can occur between addition of acid and equilibration of the reactionwith the alkali or alkaline earth carbonate. Further, the acid can beadded to the water layer 106 before addition of the alkali or alkalineearth carbonate or simultaneous with the addition of alkali or alkalineearth carbonate. Therefore, a predetermined amount of acid can be addedto the water layer 106. The quantity in moles of alkali or alkalineearth carbonate added to the water layer 106 can be readily determinedfrom the weight of alkali or alkaline earth carbonate added and themolecular weight of that carbonate. Similarly, the equivalents of acidadded can easily be determined by the mass and molecular weight of acidadded to the water layer 106. Hydrochloric acid contains one moleequivalent of acid per mole while sulfuric acid contains two equivalentsof acid per mole. In one embodiment, from about 1.5 to about 2equivalent of acid is added per mole of alkali or alkaline earthcarbonate. In another embodiment, from about 1 to about 2 equivalents ofacid is added per mole of alkali or alkaline earth carbonate. In yetanother embodiment, from about 0.5 to about 1 equivalents of acid isadded per mole of alkali or alkaline earth carbonate.

Pressurization Through Use of an Explosive Composition

The explosive composition comprising fuel and oxidant is injectedthrough one or more injection wells 122 drilled into the oil layer ofthe reservoir 102. The explosive composition must be delivered into theoil layer 102 or directly onto the oil layer 102.

Alternatively, the explosive composition can be introduced into one ormore production wells 110. The explosive composition must be placed asto maintain contact with a primer and a detonator. The primer can be anymaterial commonly used to detonate explosives including mercuryfulminate, sodium azide, lead azide, lead styphnate, or tetryl. Thedetonator can be an electrical detonator.

The water layer 106 is acidified to minimize loss of CO₂ gas throughdissolution in the water layer 106. In one embodiment, the water layer106 is acidified before addition of the explosive composition to the oillayer 102. In another embodiment, the water layer 106 is acidified afteraddition of the explosive composition to the oil layer 102. In yetanother embodiment, the water layer 106 is acidified simultaneously tothe addition of the explosive composition to the oil layer 102.

In one embodiment, the water layer 106 is acidified to a pH from about 5to about 6. In another embodiment, the water layer 106 is acidified to apH from about 4.5 to about 5.5. In yet another embodiment, the waterlayer 106 is acidified to a pH from about 3.5 to about 4.5.

In one embodiment, the explosive composition is detonated after theaddition of acid is completed. In another embodiment, the explosivecomposition can be detonated before the addition of acid is begun orcompleted. Care must be taken that the explosive blast is not so strongas to damage sensitive equipment at the site, to damage or cause thecollapse of any of the drilled well 120 and 122, or to adversely affectthe subjacent support of the surface terrain. In one embodiment, themagnitude of the explosive blast is the equivalent energy from about0.05 to about 2 metric tons of trinitrotoluene (TNT). In anotherembodiment, the magnitude of the explosive blast is the equivalentenergy from about 0.1 to about 1 metric ton of TNT. In yet anotherembodiment, the magnitude of the explosive blast is the equivalentenergy from about 0.25 to about 1.5 metric tons of TNT. In addition toserving as a source of CO₂ gas, alkali or alkaline earth carbonate mixedinto the explosive composition has the additional effect of slowing downthe explosion and cooling the temperature of the explosion as to notdamage the petroleum reservoir formation.

A single explosive detonation can potentially not be sufficient tocreate satisfactory oil production. During both the addition of acid anddetonation of the explosive composition, pressure or rate of oilproduction can be monitored at any well drilled to the oil layer 102. Ifa satisfactory pressure or rate of oil production is not obtained from afirst detonation of the explosive composition, the acts of addingexplosive to the oil layer 102, detonation of the oil layer, andmonitoring the pressure or rate of oil production can be iterativelyrepeated until a satisfactory result is obtained.

CO₂ gas is created through two events utilizing the innovationsdisclosed herein. In the first source, CO₂ gas is created by thereaction between the alkali or alkaline earth carbonate and the acidadded to the water layer 106. In the second source, CO₂ gas is createdby the detonation of the explosion through combustion and/or throughheat causing the breakdown of carbonate. The sources of CO₂ gas arereferred to as acid generation and explosive generation, respectively.CO₂ can be generated through acid generation, through explosivegeneration, or through both modes of CO₂ production. Where both acidgeneration and explosive generation are employed, the fraction of CO₂originating from either the acid generation method or the explosivegeneration method can be modified by varying the amount of explosivecomposition relative to alkali or alkaline earth carbonate injected intothe water layer 106 throughout all acts of the methods disclosed herein.In one embodiment, the ratio of the weight of carbon contained in theexplosive composition to the weight of carbon contained in the alkali oralkaline earth carbonate is about 0.4 to about 0.6. In anotherembodiment, the ratio of the weight of carbon contained in the explosivecomposition to the weight of carbon contained in the alkali or alkalineearth carbonate is about 0.2 to about 0.8. In yet another embodiment,the ratio of the weight of carbon contained in the explosive compositionto the weight of carbon contained in the alkali or alkaline earthcarbonate is about 0.05 to about 0.95.

In order to fully describe the innovations disclosed herein, acts forperforming the inventive method by reaction of acid with alkali oralkaline earth carbonate are described by reference to FIG. 2. In act202, at least one suitable production well drilled into the oil layer ofa subterranean petroleum reservoir and at least one injection welldrilled into the water layer are identified or formed. Additionalinjection and/or production wells drilled into either the oil layer orthe water layer are typically provided. In act 204, the wells drilledinto the petroleum reservoir are sealed in a manner to substantiallycontain pressure. Then, an alkali or alkaline earth carbonate and/or anacid is injected into the water layer. In act 206, the seal tosubstantially contain pressure within the reservoir is maintained tocontain CO₂ pressure throughout the performance of all downstream acts.In act 208, the remaining acts from act 204 are performed if not alreadyexecuted.

In order to fully describe the innovations disclosed herein, acts forperforming the inventive method by detonating an explosive compositionare described by reference to FIG. 3. In act 302, at least one suitableproduction well drilled into the oil layer of a subterranean petroleumreservoir and at least one injection well drilled into the water layerare identified or formed. Additional injection and/or production wellsdrilled into either the oil layer or the water layer are typicallyprovided. In act 304, the wells drilled into the petroleum reservoir aresealed in a manner to substantially contain pressure. Then, an explosivecomposition is delivered/injected into the oil layer of a petroleumreservoir and/or the water layer associated with the petroleum reservoiris acidified with acid. In act 306, the seal to substantially containpressure within the reservoir is maintained to contain CO₂ pressurethroughout the performance of all downstream acts. In act 308, theremaining acts from act 304 are performed if not already executed. Inact 310, the explosive composition is detonated, and the pressure withinthe petroleum reservoir is monitored and/or the rate of oil productionis monitored. In act 312, acts of delivering additional explosivecomposition, detonating the explosive composition, and monitoringpressure/production are repeated, if necessary.

Those having skill in the art will readily recognize that the abovesteps are only illustrative of the inventive methods disclosed herein.When the acts shown in FIGS. 2 and 3 are both performed on the samepetroleum reservoir, the order of act shown in FIGS. 2 and 3 can beperformed in any suitable order to achieve artificial CO₂ gasproduction. For example, an explosive composition can be introduced intothe oil layer and detonated before or after any alkali or alkali earthcarbonate compound is added to the water layer. Those having skill inthe art can readily identify a sequence of acts that lead to successfulCO₂ gas production. The inventive methods are not limited to a specificsequence of acts.

With respect to any figure or numerical range for a givencharacteristic, a figure or a parameter from one range may be combinedwith another figure or a parameter from a different range for the samecharacteristic to generate a numerical range. Other than in theoperating examples, or where otherwise indicated, all numbers, valuesand/or expressions referring to quantities of ingredients, reactionconditions, etc., used in the specification and claims are to beunderstood as modified in all instances by the term “about.”

While the invention has been explained in relation to certainembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thespecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as fall withinthe scope of the appended claims.

What is claimed is:
 1. A method to increase petroleum production from anoil well through the creation of carbon dioxide gas, the methodcomprising: delivering a fuel component, an oxidizer component, anemulsifying agent, and one or more of an alkali carbonate or an alkalineearth carbonate into an aqueous layer of a petroleum reservoir throughone or more injection wells drilled into the aqueous layer; sealing theoil well in a manner to substantially confine an increase in pressurewithin the petroleum reservoir; delivering an acid into the aqueouslayer through the one or more injection wells drilled into the aqueouslayer; and detonating the fuel component, the oxidizer component, andthe emulsifying agent.
 2. The method of claim 1, wherein the one or moreof alkali carbonate or alkaline earth carbonate is delivered asparticles having an average diameter of about 100 μm or less.
 3. Themethod of claim 2, wherein the alkali carbonate or alkaline earthcarbonate is further delivered as a slurry having about 5 to about 35%by weight of alkali carbonate or alkaline earth carbonate.
 4. The methodof claim 1, wherein the alkali carbonate or alkaline earth carbonate isselected from the group consisting of sodium carbonate, calciumcarbonate, potassium carbonate and magnesium carbonate.
 5. The method ofclaim 1, where the acid is a mineral acid.
 6. The method of claim 5,wherein the mineral acid comprises a solution that is from about 10 toabout 50% concentrated.
 7. The method of claim 1, wherein delivering theacid into the aqueous layer is performed before the one or more alkalicarbonate or alkaline earth carbonate is dispersed in the aqueous layer.8. A method to increase petroleum production from an oil well bycreating CO₂ gas in a petroleum reservoir having an oil layer and awater layer, wherein one or more injection wells or production wells aredrilled into the oil layer and one or more injection wells are drilledinto the water layer, the method comprising: delivering an explosivecomposition through one or more injection wells or production wells andinto the oil layer, the explosive composition capable of generating CO₂gas and comprising a fuel component, an emulsifying agent, and one ormore alkali carbonate or alkaline earth carbonate, wherein the fuelcomponent is one or more of a carbon powder and a hydrocarbon-basedcompound, delivering an acid into the aqueous layer to acidify theaqueous layer; and sealing the oil well in a manner to confine pressurebuild-up within the petroleum reservoir; and detonating the explosivecomposition.
 9. The method of claim 8, wherein the fuel component is acarbon powder.
 10. The method of claim 8, wherein the explosivecomposition comprises an the alkaline earth carbonate.
 11. The method ofclaim 8, wherein the explosive composition comprises from about 2% toabout 10% by weight of the fuel component; from about 90% to about 98%by weight of an oxidizer component; and the emulsifying agent is fromabout 4% to about 50% of the total weight of the fuel component; and theratio of alkali carbonate or alkaline earth carbonate to fuel component,oxidizer component, and emulsifying component is from about 1:10 toabout 1:2 by weight.
 12. The method of claim 8, wherein the alkalicarbonate or alkaline earth carbonate is selected from the groupconsisting of sodium carbonate, calcium carbonate, potassium carbonateand magnesium carbonate.
 13. The method of claim 8, wherein theemulsifying agent selected from the group consisting of: a) a salt of acompound having at least one hydrocarbyl group and at least onecarboxylic acid functionality; b) an alkyl-saccharide emulsifier; c)sorbitol mono-oleate; d) sodium mono-oleate; and e) the product of anacylation reaction between a hydrocarbyl group-containing carboxylicacid or carboxylic anhydride and a primary or secondary amine, whereinthe primary or secondary amine is one or more selected from Formulae I,II, III, IV, V, VI, and VII:H₂N—R  (I);R—NH—R  (II);H₂N—R—OH  (III);R′—NH—R—OH  (IV);H₂N—(RO)_(x)—H  (V);R′—NH(RO)_(x)—H  (VI); andR″NH—((CH₂)_(y)N)—R₂″  (VII); where R is a hydrocarbon group containingfrom about 1 to about 24 carbon atoms, R′ is independently either an Rgroup or an R group substituted with one or more hydroxyl groups, R″ isindependently either hydrogen, an R group, or an R group substituted byone or more hydroxyl or amino functionalities, x is from about 2 about15, and y is from about 2 to about
 10. 14. The method of claim 8,wherein the one or more of alkali carbonate or alkaline earth carbonateis supplied as one or more of an aqueous solution about 50% or moreconcentrated and particles having an average diameter of about 100 μm orless.
 15. A method to increase petroleum production from an oil well bycreating CO₂ gas in a petroleum reservoir having an oil layer and anaqueous layer, wherein one or more injection wells or production wellsare drilled into the oil layer and one or more injection wells aredrilled into the water layer, the method comprising: delivering one ormore of an alkali carbonate or an alkaline earth carbonate through theone or more injection wells drilled into the aqueous layer, wherein theone or more of alkali carbonate or alkaline earth carbonate is suppliedas one or more of an aqueous concentrated solution and particles havingan average diameter of about 100 μm or less; delivering an explosivecomposition into the oil layer, the explosive composition capable ofgenerating CO₂ gas and heat; sealing the oil well in a manner to confinepressure build-up within the petroleum reservoir; delivering an acidthrough an injection well drilled into the aqueous layer; and detonatingthe explosive composition.
 16. The method of claim 15, wherein the oneor more of alkali carbonate or alkaline earth carbonate is supplied asone or more of an aqueous solution about 50% or more concentrated andparticles having an average diameter of about 100 μm or less.
 17. Themethod of claim 15, wherein delivering acid is performed after sealingthe oil well and before detonating the explosive.
 18. The method ofclaim 15, wherein detonating the explosive composition is performedafter sealing the oil well and before delivering acid.
 19. The method ofclaim 15, wherein the explosive energy created by detonation of theexplosion composition is from about 0.05 to about 2 metric tons oftrinitrotoluene.
 20. The method of claim 15, wherein the ratio of theweight of carbon contained in the explosive composition to the weight ofcarbon contained in the alkali carbonate or alkaline earth carbonate isfrom about 0.05 to about 0.95.